Plant Adaptations, Podcast 2

Front 1

Autotrophic

Back 1

Organisms that fix inorganic compounds with energy into organic compounds (sugars).

1. Photosynthetic: take in CO2+H2O+Light = Sugar+Water (optimal at 400-700nm range)

2. Chemosynthetic: use the energy from oxidation reactions of inorganic substances to synthesize organic compounds.

Front 2

Two Reactions of Photosynthesis

Back 2

Light reaction: Photochemical reaction with chlorophyll (have magnesium molecule within compound core) in the photosystems (2 first then 1) that absorbs a photon and raises energy in order to synthesize ATP (2) and NADPH (1).

Dark reaction (Calvin-Benson cycle): Where CO2 gets incorporated into a simple sugar. Rubisco, abundant enzyme, catalyzes the fixing of carbon dioxide into phosphoglycerate which is then (with ATP and NADHP) made into glyceraldehyde-3-phosphate. G3P is then used to make glucose and starch. Most energy created in light reaction is used in the dark reaction; therefore the light reaction can be said to limit the dark reaction.

Front 3

Drawback of C3 pathway (photorespiration)

Back 3

Rubisco does carboxylation (GOOD)

It also does oxygenase (BAD)

Rubisco catalyzes the reaction between oxygen and RuBP. This wastes energy and reduces efficiency by up to 25%. Photorespiration can be increased by icnreased temperature, high oxygen, and low CO2.

Front 4

Gross and Net photosynthesis

Back 4

Gross: energy created strictly by photosynthesis

Net: Photosynthesis - Respiration

Front 5

Photosynthetically Active Radiation

Light Compensation Point

Light Saturation Point

Back 5

PAR: the amount of light available for P/S.

LCS: net p/s = 0

LSP: when p/s has reached it's threshold

Front 6

Where does P/S take place?

Back 6

In the mesophyll cells; CO2 moves in through stomata via diffusion.

Front 7

Stomatal Conductance

Back 7

Flow rate of CO2 through the stomata; based on stomata density on leaf as well as aperture (size of stomata).

Front 8

Transpiration

Back 8

When stomata are open, water vapor leaves the plant by diffusion if the humidity of the air is lower then the humidity in the leaf. This water has to be replaced so water moves from the soil, through the plant because of negative pressure; this is called water potential. Driven by a gradient of decreasing energy.

Front 9

Gravitational water

Capillary water

Hygroscopic water

Back 9

GW: more water then the soil can hold so it drains out of the root zone.

CW: ideal conditions; water potential is close to 0 with soil saturated with water as well as presence of gas bubbles.

HW: happens on hot/dry days; water saturation in soil is low which has water potential increase. This is bad; plant will wilt.

Front 10

Evolutionary Tradeoffs

Back 10

-Stomata need to be open for P/S.

-Balance between P/S and transpiration

Front 11

Aquatic Autotrophs

Back 11

Don't have stomata; instead use diffusion of bicarbonate from water column.

Front 12

Temp and its effects on P/S and C/R

Back 12

Temp up: both up

Temp more up: P/S down C/R up

Temp more up: both down

Anymore temp up: plant dies

Front 13

Tmax

Tmin

Topt

Back 13

Tmax=max temp where net ps is 0

Tmin=min temp where net ps is 0

Topt=range of optimal temperature which net carbon intake is the highest.

Front 14

Dissipation of heat from the plant

Back 14

Evaporation: water evaporating (liquid to gas) will have a lot of thermal energy lost. The higher rate of transpiration the great the evaporative cooling.

Convection:

Front 15

Plant Adaptations

Back 15

Evap and Convec for cooling.

In water high locations, tranpsiation is the main method to remove heat with stomata open most of the time.

Constraints for plants; light, temperature, humidity, water, wind

-Ex: desert landscape, high heat, high light, low humidity, low water, and high rate of transpiration.

Front 16

Plants distribute sugar to different parts of the plant

Back 16

Provide sugars where the plant can maintain a positive carbon balance to survive and reproduce (P/S > Respiration)

Front 17

Water demand and Temperature

Back 17

Plants open and close stomata depending on conditions. Closed during hot/dry times. Open during cooler/sunny/humid times (early morning).

Front 18

Modifications of P/S

Back 18

C4 pathway (scarce water): have mesophyll cells and bundle sheathes. Use enzyme PEP carboxylase which has lower affinity for oxygen. carbon fixed into malate in the mesophyll. then malate into bundle sheaths with rubisco to make sugars. process keeps oxygen out of bundle sheaths allowing for less photorespiration --> keep stomata closed.

CAM: similar to c4 but steps are seperated temporally and not spacially. stomata open at night; co2 taken in. convert to malic acid using PEP. malic acid accumulates in mesphyll cells. close stomata during day in order to not lose water. convert malic acid to carbon dioxide. then co2 is pushedi nto hte c3 pathway to fix carbon dioxide into sugars.